The present invention relates to injectors with subdivided pressure convertors or multipliers.
Injectors are utilized in fuel injection system for injection of fuel under high pressure into combustion chambers of internal combustion engines with direct injection. The injection start and the injection quantity are adjusted with the injectors. The injectors are located at the position of the previously utilized nozzle holder combinations. The injectors can be used without significant modifications of cylinder heads of the internal combustion engines. The injectors can have pressure multipliers, with which a primary pressure at the inlet side can be significantly increased.
German patent document DE 198 35 494 A1 discloses a pump-nozzle unit. It supplies the combustion chamber of an internal combustion engine with fuel under high pressure. A pump unit serves for building up an injection pressure, so that the fuel can be injected via an injection nozzle into combustion chamber of an internal combustion engine. Furthermore, a control valve connected with a control unit is provided, which can be formed as an outwardly open A-valve. A valve actuating unit controls the pressure buildup in the pump unit. For providing a pump-nozzle unit with a control unit which has a simple construction, is small and has in particular a short response time, it is proposed to form a valve actuating unit as a piezo-electric actuator. In this pump-nozzle unit, a valve actuating unit is associated with a single-part hydraulic multiplier. It serves in a corresponding design for transmission of a small expansion movement of the actuator into a great valve actuating movement.
Accordingly, it is an object of the present invention to provide an injector with a subdivided pressure convertor or multiplier which is a further improvement of the existing injectors.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in an injector with a subdivided pressure multiplier in which the pressure multiplier is formed as a two-part piston arrangement.
With the inventive two-part design of the pressure multiplier, a simple construction can be provided, so that a cost-favorable production is guaranteed. When the pressure multiplier which is composed of two piston elements, is formed so that a radial play is provided with respect to the opening of the injector housing which receives the piston, then an expensive manufacture of a one-part piston which requires high manufacturing tolerances can be avoided. The subdivision of the piston element into two individual pistons allows, due to a subdivision of the housing which receives the pistons, a cost favorable manufacture both of the individual pistons which operates as a pressure multiplier, as well as two-part housing.
The both pistons, of which one piston forms limiting surface of a control chamber in which a control pressure acts, while the other piston extends with an end side into a pressure chamber, are spread or in other words pre-tensioned for making difficult the separation at the contact surfaces by a spring element. It is therefore guaranteed that the pistons do not separate during an axially extending stroke movement.
The individual pistons of the piston arrangement are pretensioned relative to one another in an axial direction, to avoid separation of the pistons during the stroke on their contact surfaces. For compensation of mounting tolerances, to the contrary the individual pistons are received with a play relative to one another. In other words the outer individual piston is guided in the upper housing half, while the inner piston is guided in its lower housing half with a plate. Thereby the housing tolerances and manufacturing tolerances of the components are compensated, so that the manufacture of the pressure multiplier together with the housing can be achieved in a substantially most cost-favorable manner.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.